Deposits of valuable fluids, such as crude oil, natural gas and even water, frequently occur in geologic formations having limited permeability. Although the initial perforating of the sides of an oil well typically opens up this type of deposit for initial exploitation, the well may soon experience a drop in production and require further treatment. To address this situation, a number of different fracturing techniques have been developed including explosive fracturing, hydraulic fracturing and high energy gas fracturing (HEGF). Each of these techniques is designed to fracture the underground geologic formation, thereby increasing permeability.
HEGF appears to have an advantage over the other fracturing techniques when certain conditions exist in a well. Test observations have shown that HEGF can create several radially extending fractures, thereby increasing the chance of significantly increasing permeability of nearby rock.
One type of HEGF uses a propellant that must be kept dry and contained during combustion. In this version, a strong container bearing a charge of propellant (i.e. a low explosive) is lowered into a partially liquid filled well and the propellant is ignited. The container keeps the charge dry and constrains it to obtain the full explosive force.
Until recently, the container for the propellant charge has been torn apart in the blast. Unfortunately, this has resulted in debris being left in the well, sometimes in the form of pieces that were large enough to create problems in the further exploitation of the well.